1. Field of Invention
The invention relates to a method of developing a configuration for encoding a data glyph block such that the data capacity of the data glyph block is maximized or made optimal. The invention also relates to a method of embedding a data glyph block containing occlusions into an image by halftone rendering of glyph marks, again preferably with the data glyph block having maximal or optimal data capacity.
2. Description of Related Art
It is often desirable to have a document contain not only human readable information, but also machine readable information. For example, a check may desirably contain machine readable identification verification.
An example of such machine readable information is a bar code. However, bar codes are obtrusive and not esthetically pleasing in a document. Therefore, self-clocking glyph codes have been developed in order to embed digitized information within a document in an esthetically pleasing manner. One of the principal advantages of self-clocking glyph codes is that they tend to be esthetically pleasing because of their non-obtrusive visual appearance.
When a data glyph block is written onto a document, it typically forms a uniformly monochromatic (e.g., gray) or polychromatic block upon the document. The glyph marks within the block are not obtrusive to the unaided human eye, thus making the block of embedded data have an esthetically pleasing appearance as opposed to, for example, the more obtrusive bar code.
A data glyph block may contain not only active data areas, i.e., areas where the cells of the data glyph block contain user data, but also may contain one or more occlusions, i.e., areas not containing user data. For example, in order to make the rendered data glyph block inconspicuous upon an artifact, it is often desirable to intentionally include human visible/readable information within the data block, for example to include logos, icons, graphics, text, marks or other objects within the data block. See, for example, co-pending application Ser. No. 09/401,539, filed on even date herewith, entitled xe2x80x9cMethod Of Encoding Embedded Data Blocks Containing Occlusionsxe2x80x9d(Petrie), incorporated herein by reference in its entirety. The embedded data block would then appear to be background to the human visible/readable information. However, the human visible/readable information obscures numerous areas of the data glyph block, rendering these areas to occlusions and reducing the data areas and overall data capacity of the data glyph block.
It is also possible to form images themselves utilizing the glyph marks of a data block as the cells making up the image. This is done by the known method of halftone rendering of the glyph marks, for example as described in U.S. Pat. No. 5,315,098 (Tow) and U.S. Pat. No. 5,710,636 (Curry), both incorporated herein by reference in their entireties. In forming such an image, the gray level, or grayscale, values of the glyph marks is varied, for example by making the glyph symbols (for example xe2x80x9c/xe2x80x9d and xe2x80x9c xe2x80x9d) thicker/darker or thinner/lighter as needed. The overall image formed contains the machine readable embedded data therein, but again the individual glyph marks are not obtrusive to the unaided human eye.
However, the halftone rendering of the data glyph block results in the formation of occlusions comprised of numerous cells within the data glyph block, for example because the cells must be rendered too dark or too light, for integrity of the image, to be recognized by a decoder.
It is an object of the present invention to configure and reliably encode a data glyph block containing occlusions such that the data capacity of the data glyph block is optimized.
It is a still further object of the present invention to form an image with a data glyph block. It is also an object of the invention to optimize the data capacity of an image-forming data glyph block without degrading the quality of image formed.
These and other objects are achieved in the present invention by a method of developing a configuration of a data glyph block containing occlusions and having an optimized data capacity, and encoding such configuration.
These and other objects are also achieved in the present invention by a method of forming a halftone image from a data glyph block containing occlusions. Preferably, the configuration of the data glyph block is such that the data capacity of the data glyph block is optimized against the integrity and quality of the image to be formed.